Oscillator tube cavity tuner



June 26, 1956 E. G. MARTIN 2,752,524

OSCILLATOR TUBE CAVITY TUNER Filed Dec. 13, 1945 30 I ,7 l E 5 F" :E

33 32 FIG. I

INVENTOR EDWARD G. MARTIN ATTORNEY United States Patent OSCILLATOR TUBE CAVITY TUNER Edward G. Martin, Cambridge, Mass, assignor, by mesne assignments, to the United States of America as rep= resented by the Secretary of the Navy Application December 13, 1945, Serial No. 634,846

Claims. (Cl. 315-5) This invention relates to tuning apparatus, and more particularly to apparatus for tuning annular cavity resonators.

In apparatus employing a McNally type velocity modulated electron tube or other type electron tube with a resonant cavity partially internal and partially external to the tube, it is frequently desirable to provide means for tuning the external portion of the cavity. This can be accomplished by a flexible diaphragm, variable paddles, adjusting slugs, or other means of changing the volume of the cavity. However, this type of tuning is often unsatisfactory because of the difiiculty in arriving at the desired tuning point rapidly. Also, in clamping the external portion of the cavity to the external electrode leads of the tube, these external leads are stressed and frequently deformed.

It is, therefore, an object of this invention to provide a tuning apparatus for such cavities which is simple, compact, and rapid and positive in operation.

A further object of this invention to provide means for preventing deformation of the external annular electrode leads of such a tube when clamped in a cavity structure.

Other objects and advantages of this invention will be apparent from the following specification, when taken with the accompanying drawing, in which:

Fig. 1 shows a cross section of one form of the invention; and,

Fig. 2 is a plan view of insulation spacers, used in the invention; and,

Fig. 3 is an end elevation of a tuning plunger forming a part of the invention.

The embodiment shown is particularly adaptable to tuning a McNally type velocity modulated electron tube by varying the dimensions of a cavity external to the tube. This comprises, means generally designated partially defining the resonant cavity, a nut 11 rotatably supported in means It) by bearing means 12, an annular tuning plunger 13, and a supporting cylinder 14 coaxial with and attached to means 10. Means 15, in this embodiment a key 30, cooperates with cylinder 14 for preventing rotary motion of plunger 13. Control means 32 causes nut 11 to rotate, thereby tuning cavity 18.

The McNally tube 19 inserted in the tuning apparatus has a plurality of electrodes 20 and 21 extending transversely through the tube. These electrodes are usually annular, and provide boundary surfaces for the cavity, and cooperate with means 10 to completely enclose cavity 18. Cylinder 14 in combination with an annular plate 52 clamps together the annular portions of electrodes 20 and 21 external to the tube envelope, and thereby properly positions tube 19 in the tuning apparatus. To protect these external portions of the electrodes from stress and deformation, spacers 22 and 23 made of insulating material are positioned between the external portions of the electrodes.

It is, therefore, apparent that tube 19 is so positioned Patented June 26, 1956 ICC in the tuning apparatus that annular plate 52 is in contact with the external portion of the electrode 20, and supporting cylinder 14 is in contact with the external portion of the. other electrode 21, thereby clamping these external portions of the electrodes toward one another. However, the electrodes are protected by the insulation spacers 22, 23, which preferably form an axially split cylinder, as is best shown in Fig. 2.

Cavity structure 10 includes a cavity barrel 24 which defines the peripheral boundary of cavity 18. Annular plate 52 is attached to cavity barrel 24, and partially defines a boundary wall of the cavity. Annular tuning plunger 13 is positioned in one end of cavity barrel 24' and is free to move axially in the cavity. This plunger partially defines a second boundary Wall of cavity 18, and is adapted to engage the threads of nut 11. Cavity barrel 2'4 in combination with tuning plunger 13 and plate 52 cooperate with tube electrodes 20 and 21 to completely enclose the resonant cavity. Axial movement of plunger 13 changes the volume of the cavity and thereby tunes it.

Bearing means 12. supports nut 11 coaxially in cavity barrel 24. This means comprises a ball bearing 26 having an inner race cut in nut 11, and an outer race formed by axially spaced rings 27 and 28, urged together by a circular spring 29, thereby holding the balls of the ball bearing in snug relation to both races.

Means 15 cooperating with cylinder 14 comprises a key 30 positioned in a keyway (see 51 in Fig. 3) of cylinder 14 and operating in a slot cut in plunger 13. This key prevents rotary motion of plunger 13, so that when nut 11 is turned, plunger 13 moves axially in the cavity barrel.

Nut 11 is attached to an annular flange gear 16, meshing with a pinion 17 carried by a shaft 31 having a tuning knob 32. Adjustment of knob 32 moves plunger 13, thereby tuning the cavity.

Tuning plunger 13 has an axial slot 50 (see Fig. 3) cut in it, so that coupling means 33 can couple electromagnetic energy between the cavity and an external cir cuit. In the present case coupling means 33 comprises a loop (see Fig. 1), led into cavity 18.

It is to be understood that while this invention has been described as using a McNally type velocity modu lated tube it is not limited thereto. As is apparent, this invention is adaptable for use with any electron tube which employs a resonant cavity partially external to the tube envelope.

This invention is to be limited only by the appende claims.

What is claimed is:

l. A tunable annular cavity resonator comprising, a hollow cavity barrel defining the peripheral boundary of said annular cavity resonator, a supporting cylinder coaxial with and attached to said cavity barrel, a nut disposed in said cavity barrel, means for rotatably supporting said nut coaxially in said cavity barrel, an annular tuning plunger located in one end of said cavity barrel and free to move axially in said cavity barrel, said tuning plunger partially defining a boundary wall of said annular cavity and adapted to engage the threads of said nut, an annular end plate for said cavity barrel and said tuning plunger for completing said cavity, locking mechanism in said supporting cylinder for preventing rotary motion of said tuning plunger, and adjusting means to rotate said nut to impart axial motion to said tuning plunger, thereby tuning said cavity.

2. Apparatus in accordance with claim 1 in which said means for supporting said nut coaxially in said cavity barrel is a ball bearing comprising an inner race cut in said nut, an outer race formed by axially spaced rings, and a circular spring adapted to exert a force urging said rings together and thereby holding the balls of said ball bearing in snug relation to both said races.

3. A tuned cavity resonator for a reflex velocity modulated tube oscillator having an electron discharge device with cavity defining electrodes extending transversely through the envelope of said tube, said tuned cavity resonator comprising, an annular cavity structure adapted to be removably mounted external to said tube, means for adjusting the volume of said structure, means for clamping said structure to the external portion of said electrodes to complete said cavity resonator, and insulating spacers adapted to be positioned externally of said tube envelope between said electrodes to prevent deformation of said electrodes by said clamping means.

4. A tuned cavity resonator for a reflex velocity modulated tube oscillator having an electron discharge device with cavity defining electrodes extending transversely through the envelope of said tube, said tuned cavity resonator comprising an annular cavity structure adapted to be removably mounted external to said tube, a lead screw and gear train assembly for manually varying the volume of said cavity, means for clamping said structure to the external portion of said electrodes to complete said cavity resonator, and semi-circular insulating spacers adapted to be positioned externally of said tube envelope between said electrodes to prevent deformation of said electrodes by said clamping means.

5. A tuned cavity resonator for a reflex velocity modulated tube oscillator having an electron discharge device with cavity defining electrodes extending transversely through the envelope of said tube, said tuned cavity resonator comprising, an annular cavity structure adapted to be removably mounted external to said tube, a movable plunger adapted to vary the volume or" said cavity, a lead screw and gear train assembly for manually adjusting the position of said plunger, means for clamping said structure to the external portion of said electrodes to complete said cavity resonator, and semi-circular insulating spacers adapted to be positioned externally of said tube envelope between said electrodes to prevent deformation and stressing of said electrodes by said clamping means.

References Cited in the file of this patent UNITED STATES PATENTS 2,183,215 Dow Dec. 12, 1939 2,251,085 Unk July 29, 1941 2,284,405 McArthur May 26, 1942 2,304,186 Litton Dec. 8, 1942 2,402,443 Peterson June 18, 1946 2,404,279 Dow July 16, 1946 2,406,850 Pierce Sept. 3, 1946 2,442,671 Tompkins June 1, 1948 2,488,906 Gardner Nov. 22, 1949 2,496,535 Hoglund et al Feb. 7, 1950 2,525,806 Kurnpfer Oct. 17, 1950 

